As crude oil prices rise, all downstream products become more expensive—for example fuel for heating, power stations and vehicles, especially ships.
More highly refined or “lighter” fuels are more expensive than less highly refined or “heavier” fuels. The latter tend to be less favoured for use. They are more viscous and tend to burn “dirtier”. They are more prone to separation or sedimentation during transportation, blending or storage. By “dirtier”, we mean that the less highly refined fuels contain a higher concentration of unstable components or compounds than more highly refined fuels. Such components or compounds promote the formation of sediment or sludge within the fuel. Further, it is believed that such components or compounds lead to deleterious carbon formation on combustion, leading, inter alia, to deposition on fuel injector, combustion and reduced efficiency in waste heat recovery.
It many commercial haulage sectors the fuel cost is a major part of the total operating cost. In the case of commercial shipping, for example, it is estimated that the fuel cost sometimes amounts to 70% of the total operating cost of the ship.
Therefore there is often a strong economic driver to move to less refined fuels but the adverse consequences, mentioned above, inhibit it. Ship operators, for example, cannot tolerate addition down-time whilst ships' engines and associated equipment are cleaned of soot (i.e. carbon) deposits. Moreover many ships cannot have visible smoke exhaust streams. This would be unacceptable on cruise ships, and may in any case not satisfy environmental laws in countries, which ships may dock.
Blended fuels—for example conventional diesel and bio-diesel, and different grades of conventional fuel oil—may also suffer from problems of instability. This is a particular problem when ships buy fuel on the spot market, and the purchased fuel is added to fuel remaining in its fuel store. The result may be problems in pumping and/or combustion.
It would be desirable to have an additive composition which reduces or overcomes such problems.